Fossil based power plants are facing a more and more variable operating regime as response to the increasing installed capacity of renewable electricity power units and as a consequence of seasonal and daily electricity demand variation.
Especially combined cycle power plants (CCPP's) are operated in an extremely cycling mode and in some cases CCPP's are shut down and restarted daily.
The cost of electricity of a power plant based on a gas turbine and equipped with a carbon dioxide capturing system is significant. The electricity prices vary depending on if the demand is high or low. When a lot of industries are closed for the day or not running at full capacity, e.g. during night time, the electricity prices are decreased. When the industries are working at full capacity, e.g. during day time, the electricity prices are increased due to the high demand.
A typical gas turbine, such as a gas turbine in a gas turbine plant for power generation, comprises a compressor for compression of inlet air, a combustor where the compressed air is mixed with fuel and where the mixture is ignited, and a turbine where exhaust gas from the combustor is expanded.
Exhaust gas emitted from a gas turbine generally comprises pollutants of environmental concern, such as carbon dioxide (CO2).
The exhaust gas from a gas turbine generally comprises SOx and other impurities and contaminants.
When a fossil based power plant is equipped with a carbon dioxide capturing system and the carbon dioxide capturing system is in operation the energy increase needed is substantial compared to power plant without a carbon dioxide capturing system. The power output compared to the equivalent thermal input is reduced by 15-20%, i.e. a power penalty of 15-20%, when a power plant comprising a carbon dioxide capturing system instead of a power plant not comprising a carbon dioxide capturing system. If the carbon dioxide capturing system was to be switch off the power penalty would be much lower.
It is concluded that there is a need for improving the flexibility of operation and electricity consumption of power plants based on gas turbines and equipped with carbon dioxide capturing systems.